TL;DR
A shutdown survey is performed while the asset is de-energised, isolated and cooled during a planned outage, so the team can reach internals and achieve the tightest tolerances; an operational survey is performed while the plant runs, trading some access and accuracy for zero production loss. The choice is not about which is more accurate in a vacuum — it is about whether the measurement you need can be taken safely and meaningfully while the equipment is hot, moving and live. This guide compares both on access, achievable tolerance, cost, timing and risk, with a decision table for Australian mining and processing sites.
Key takeaways
- A shutdown survey buys you physical access to isolated internals and a thermally stable structure, enabling cold-state tolerances down to 0.1-0.5 mm on mill trunnions, kiln tyres and crane rails — accuracy an operational survey on a hot, vibrating asset cannot match.
- An operational survey costs nothing in lost production, but production downtime on a Pilbara iron ore line or a Gladstone alumina train runs from roughly AUD 50,000 to well over AUD 500,000 per hour, so the "free" operational option is often the commercially correct one when it can deliver the data.
- Shutdown windows are fixed and unforgiving; ISS routinely runs 12-hour shift crews with a Leica RTC360 and a Leica TS60 monitoring total station so a kiln or SAG mill survey closes inside the outage rather than holding up restart.
- Operational surveys lean on stand-off methods — drone photogrammetry under CASA Part 101, terrestrial scanning from walkways, and robotic-total-station deformation monitoring — because nothing can touch a live, moving asset.
- Most production assets need both over their life: operational surveys for trending and condition monitoring between outages, and a shutdown survey at the outage to capture the cold, isolated geometry that drives the repair decision.
Table of contents
- What is a shutdown survey?
- What is an operational survey?
- Access: the dividing line
- Accuracy: hot, moving and live vs cold and isolated
- Cost: survey fee vs downtime
- Timing, safety and standards
- Decision table: which survey for your asset?
- Why most assets need both
- Frequently asked questions
- What to do next
What is a shutdown survey?
A shutdown survey (also called a turnaround, outage or TAR survey) is any dimensional or positional measurement carried out during a planned production outage, while the asset is isolated, locked and tagged out, depressurised and — where it matters — cooled to a stable temperature. The defining feature is access. With the asset stopped and isolated, the survey crew can stand inside a ball mill, reach a kiln girth gear, or sit a scanner directly under a stacker boom without a live process between them and the target.
Typical shutdown survey scopes in the Australian resources sector include SAG and ball mill trunnion and girth-gear alignment, rotary kiln axis and shell ovality checks at cement and alumina plants, crusher and screen as-builts, conveyor structure straightness, crane rail gauge and elevation surveys, and tie-in dimensional control for new spools and equipment being installed during the window. Deliverables tie to GDA2020 / MGA2020 horizontally and AHD vertically where the asset sits in a site control network, and to local machine datums for alignment work.
The constraint is the clock. The outage has a fixed length, every hour costs production, and the survey competes with mechanical, electrical and inspection trades for the same access. A shutdown survey is therefore as much a logistics exercise as a measurement one.
What is an operational survey?
An operational survey is performed while the plant keeps running. Nothing is isolated, the equipment may be hot and rotating, and the survey team works from a safe stand-off — walkways, platforms, the ground, or the air. Because you cannot place a target on a moving trunnion or stand inside a live kiln, operational surveys rely on non-contact and remote methods.
Common operational scopes include stockpile and pit volumetrics by drone, structural deformation monitoring of headframes, bins, tailings dam walls and conveyor galleries, thermal-state ("hot") kiln alignment using the running shell, and progressive as-built capture of brownfield areas around live plant. The toolset is built for distance and repeatability: DJI Matrice-class UAVs flown under CASA Part 101 for photogrammetry and corridor mapping, FARO and Leica terrestrial scanners run from accessible standpoints, and automated Leica or Trimble robotic total stations locked onto fixed prisms for continuous deformation monitoring between outages.
The win is obvious — production never stops. The trade-off is equally real: you measure what you can see and reach from a distance, on a structure that is thermally expanded and vibrating, so achievable tolerance and completeness are lower than the same job done cold during a shutdown.
Access: the dividing line
Access is the single factor that most cleanly separates the two. It decides what you can physically measure, and it drives almost every downstream difference in accuracy and method.
| Access factor | Shutdown survey | Operational survey |
|---|---|---|
| Internal access | Full — crews enter mills, kilns, vessels, crushers | None — internals are off-limits while running |
| Contact targeting | Yes — prisms and adhesive targets on the asset | No — non-contact only on live/moving plant |
| Line of sight | Optimised by removing covers, scaffolding to suit | Limited to existing walkways, ground and air |
| Competing trades | Heavy — shares the window with mechanical/E&I | Minimal — survey works around production |
| Isolation/LOTO | Required, formal permit | Not applicable to the running asset |
During a shutdown the team can scaffold to the exact viewpoint, pull an inspection cover to scan a bearing, and bolt a prism to a structure for a repeatable monitoring baseline. Operationally, you are constrained to whatever sightlines the live plant already offers, which is why drone photogrammetry and long-range scanning carry so much of the operational workload — they reach what a person on a walkway cannot.
Accuracy: hot, moving and live vs cold and isolated
Two physical effects degrade an operational measurement relative to a shutdown one: thermal expansion and motion.
A rotary kiln shell at running temperature can sit 200-400 degC above ambient; carbon steel expands roughly 12 micrometres per metre per degree, so a 4 m diameter shell can grow several millimetres on the diameter and a 60 m kiln can stretch tens of millimetres along its axis. A hot kiln alignment captures the real running geometry — which is exactly what you want for some decisions — but it cannot be compared like-for-like against a cold as-built drawing. A cold shutdown survey, taken once the shell has stabilised below about 40 degC, gives you the reference geometry the mechanical fitters actually set to.
Motion compounds it. You cannot achieve a tight discrete-point tolerance on a rotating trunnion or a vibrating conveyor drive while it runs. Robotic total stations doing operational deformation monitoring deliver excellent relative repeatability — sub-millimetre on a fixed prism over time — but that is monitoring movement, not setting a cold machine alignment.
| Measurement | Shutdown (cold, isolated) | Operational (hot/running) |
|---|---|---|
| Mill trunnion / girth gear alignment | 0.1-0.5 mm achievable | Not feasible on a turning mill |
| Kiln axis and ovality | Cold reference geometry | Hot running geometry only |
| Crane rail gauge and level | 0.5-1 mm (Leica TS60) | Limited to off-crane stand-off |
| Structural deformation trend | Baseline at known cold state | Sub-mm relative repeatability over time |
| Stockpile / pit volume | Possible but rarely needs an outage | Drone photogrammetry, no production loss |
The honest framing: a shutdown survey wins decisively on cold-state, contact, single-point accuracy. An operational survey wins where the question is "how is this moving over time?" or "how much material is in this stockpile?" — questions you should never stop production to answer.
Cost: survey fee vs downtime
This is where the comparison flips for many managers. The survey fee is rarely the deciding number.
ISS field rates are broadly consistent whether the work is operational or shutdown: a scanning or dimensional-control crew runs in the order of AUD 2,500-4,500 per day, with shutdown work attracting shift and after-hours premiums of 25-50% because outages run around the clock. So a two-shift, two-day shutdown survey might cost AUD 15,000-30,000 in survey fees.
Now weigh that against production. Downtime on a major Pilbara iron ore train, a Gladstone alumina refinery line, or a Bowen Basin coal handling plant is measured in tens to hundreds of thousands of dollars per hour. If the data can be obtained operationally without stopping anything, the operational survey is not just cheaper — it avoids a downtime cost that dwarfs the survey fee entirely.
| Cost factor | Shutdown survey | Operational survey |
|---|---|---|
| Survey crew fee | AUD 2,500-4,500/day + 25-50% shift premium | AUD 2,500-4,500/day |
| Production loss | Shares the outage cost; restart pressure | None |
| Access provision | Scaffolding, LOTO, permits (site cost) | Minimal |
| Schedule risk | High — fixed window, overrun cascades | Low — reschedulable |
| Drone mobilisation | Rarely the primary method | Cost-efficient over large areas |
The commercial rule of thumb: if the measurement only needs to be done when the asset is stopped, fold it into a planned outage and never create a survey-only shutdown. If it can be done operationally to the required tolerance, do that and keep the plant running.
Timing, safety and standards
Shutdown surveys live and die on the schedule. The window is fixed, cooldown eats into it (a kiln may need 12-24 hours to reach a stable cold state), and the survey competes with every other trade for access. ISS plans shutdown work backwards from restart: confirm isolation and cooldown timing, scaffold to suit, run 12-hour shift crews if needed, and report preliminary results on site before demobilising so the repair decision is not waiting on the office.
Safety governs both modes but in different ways. Shutdown work means formal isolation, lockout/tagout, confined-space entry permits and hot-work coordination. Operational work means stand-off from live, energised and moving plant, and — for any UAV component — compliance with CASA Part 101, a remote pilot licence (RePL) and an operator's certificate (ReOC), plus site-specific approvals for flying over active operations. Both modes are delivered to AS/ISO-aligned quality procedures, with instruments carrying current calibration certificates (within 12 months), and spatial results referenced to GDA2020 / MGA2020 and AHD where the asset is tied to site control.
Decision table: which survey for your asset?
| If your priority is… | Choose | Why |
|---|---|---|
| Cold machine alignment (mill, kiln, crusher) | Shutdown survey | Needs isolation, cooldown and contact targeting |
| Internal as-built of a vessel or mill | Shutdown survey | Internals are only reachable when stopped |
| Tie-in control for new equipment | Shutdown survey | Installation happens inside the outage |
| Stockpile or pit volume | Operational (drone) | No reason to stop production |
| Deformation trend over months | Operational monitoring | Repeated remote measurement, plant stays live |
| Hot running geometry of a kiln | Operational (hot align) | Captures real thermal state |
| Lowest commercial cost overall | Operational if it meets tolerance | Avoids downtime that dwarfs survey fees |
| Tightest single-point tolerance | Shutdown survey | Cold, stable, contact measurement |
Work down from the measurement, not the method. Define the tolerance and the deliverable first; the access and thermal state that data requires will tell you whether it is a shutdown or operational job.
Why most assets need both
A producing mill, kiln or crane handling line is not a one-survey-and-done proposition. Over an asset's life the two survey types interlock:
- Between outages, operational surveys do the watching — drone volumetrics on feed stockpiles, robotic-total-station monitoring of a tailings dam wall or a settling headframe, and progressive brownfield as-builts around live plant. These flag drift early, while production continues.
- At the outage, a shutdown survey captures the cold, isolated truth — trunnion alignment, kiln ovality, crane rail geometry, tie-in dimensions — that the operational trend cannot reach and that the repair scope depends on.
- The trend informs the outage. Operational monitoring that shows a structure moving, or a wear pattern accelerating, lets you scope the next shutdown survey precisely, so the limited outage window is spent on the assets that actually need it.
Used together, the operational survey tells you when and where to look, and the shutdown survey tells you exactly what to fix.
Frequently asked questions
Is a shutdown survey always more accurate than an operational survey?
For cold-state, single-point alignment work, yes — isolation, a stable temperature and contact targeting let a shutdown survey reach 0.1-0.5 mm on a mill or crane rail, which a hot, moving asset cannot match. But for measuring movement over time, operational robotic-total-station monitoring delivers sub-millimetre relative repeatability, and for stockpile volumes a drone survey is both accurate enough and far cheaper because it avoids downtime. Accuracy depends on the question, not just the mode.
Can a kiln or mill be surveyed while it is running?
A rotary kiln can be hot-aligned while running to capture its real thermal-state geometry, using the rotating shell — that is a recognised operational technique. A mill's trunnion and girth-gear alignment, however, needs the mill stopped, isolated and cooled; you cannot achieve a tight contact alignment on a turning mill. So the answer is method-specific: hot alignment runs operationally, cold alignment needs a shutdown.
When is an operational survey the better commercial choice?
Whenever the required data can be obtained to tolerance without stopping the asset. With downtime on major Australian resource lines costing from roughly AUD 50,000 to over AUD 500,000 per hour, an operational survey that delivers the answer — stockpile volumes, deformation trends, brownfield as-builts — avoids a downtime cost that far exceeds the survey fee. Reserve shutdowns for measurements that genuinely require isolation.
How do you fit a shutdown survey inside a fixed outage window?
By treating it as a logistics task. ISS plans backwards from restart, confirms cooldown and isolation timing, scaffolds to the exact viewpoints, deploys a Leica RTC360 for rapid capture plus a Leica TS60 for precision points, runs 12-hour shift crews where the schedule demands it, and delivers preliminary on-site results before demobilising so restart is never held up waiting on a report.
Do drone surveys of a live site need special approval?
Yes. Any UAV work over an operating site in Australia is flown under CASA Part 101, by a pilot holding a remote pilot licence (RePL) under an operator's certificate (ReOC), and typically requires site-specific approval to fly over active operations, plant and personnel. ISS holds the certifications and coordinates the site approvals as part of mobilisation.
What to do next
Choosing between a shutdown survey and an operational survey comes down to three questions: does the measurement need the asset cold and isolated, what tolerance does the deliverable demand, and what would stopping production actually cost?
- Define the deliverable and tolerance first. Cold alignment and internal as-builts point to a shutdown survey; volumes, trends and brownfield capture point to an operational survey.
- Price the downtime, not just the survey. If the data can be captured operationally to spec, you almost certainly save far more than the survey fee.
- Scope the outage from the trend. Use operational monitoring between shutdowns to target the next outage survey precisely.
If you are weighing a shutdown survey vs an operational survey for a mill, kiln, crane line or processing plant, call ISS on 0407 057 015. We will assess your asset, tolerances, outage schedule and access, and recommend the approach — operational, shutdown, or both — that gets you the right data for the least production impact.